This application claims the priority of Japanese application 8-257123, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a rotating position detecting device using a magneto-electric converter element such as a Hall Effect element, and more particularly to an internal combustion engine rotating position detecting device for detecting a position of a crank angle internal combustion engine.
In the past, a rotating position detecting device using a magneto-electric converter element such as a Hall Effect element has been composed of a main body of a rotating position detecting device having a magnetoelectric element and a magnet for supplying a magnetic field to the magneto-electric element in a case and a detected rotating body having projections or grooves rotating together with a crank shaft of an engine. The main body of rotating position detecting device and the detected rotating body were arranged in opposite positions. Changes in magnetic flux density generated by rotation of the detected rotating body based on the shape of the projections or grooves on the detected rotating body were detected and formed in a rectangular wave-form by the main body of rotating position detecting device. A crank position was detected by measuring high level and low level time periods of the rectangular wave-form, and the measured result was used for control of the internal combustion engine.
FIG. 6 shows a known detected rotating body 3 in the conventional rotating position detecting device described above. The detected rotating body 3 had four projections 3a in the periphery, and a width .theta..sub.0 of the projection 3a is detected for control of an internal combustion engine.
The lines (f).about.(h) in FIG. 7 show change in magnetic flux density generated by rotation of the known detected rotating body 3 of FIG. 6 and rectangular signals detected based on the change in magnetic flux density. The line (f) shows the change in magnetic flux density A over time in the abscissa acting on the magneto-electric converter element. Referring to the line (f) of FIG. 7, the magnetic flux density Aa shows a state of magnetic flux density generated where a gap (hereinafter, referred to as "air gap") between the top front of the rotating position detecting device (the magneto-electric converter element) and the detected rotating body 3 is narrow, and the magnetic flux density Ab shows a state of magnetic flux density generated where the air gap is wide. The lines (g) and (h) in FIG. 7 show detected rectangular wave-forms B, C generated at the time when the generated magnetic flux densities Aa, Ab are at a threshold voltage V.sub.1 '. It can be understood from the lines (f), (g) and (h) that the generated magnetic flux density Aa or Ab varies when the air gap varies, and the width (period) of the detected rectangular wave-form .theta..sub.1 or .theta..sub.2 has a different shape when the threshold voltage V is kept constant. That is, FIG. 7 shows that the width of the detected signal wave-form .theta..sub.1 or .theta..sub.2 varies as the generated magnetic flux density Aa or Ab varies.
The prior art of controlling an internal combustion engine by detecting the high-level or low-level width (period) .theta..sub.1 and .theta..sub.2 of a rectangular wave-form as described above is disclosed, for example, in Japanese Patent Application Laid-Open No. 1-240751.
In the prior art rotating position detecting device using a magneto-electric converter element such as a Hall Effect element, variation in the air gap between the detected rotating body and the top front of the rotating position detecting device (the magneto-electric converter element) inevitably occurred due to an arrangement error caused by the construction of the device when the detected rotating body and the magneto-electric converter element are assembled.
Detecting the high level and the low level widths (time periods) .theta..sub.1 and .theta..sub.2 of the rectangular wave-form is equivalent to detecting the width of the projection or the groove of the detected rotating body. In the prior art, the difference in the gap between the top front of the rotating position detecting device (the magneto-electric converter element) and the detected rotating body, that is, the variation of the air gap was not taken into consideration, and as a result, the output signal of the rectangular wave-form undesirably varied because of the air gap. Accordingly, a crank angle (rotating position) could not accurately be detected.
The present invention has the objective of overcoming the above-mentioned problems. An object of the present invention is to provide a rotating position detecting device capable of detecting a rotating position with high accuracy even if a variation exists in the air gap between the detected rotating body and the magneto-electric converter element (the rotating position detecting device), and is capable of widening a permissible range of the gap variation.
In order to achieve the above-mentioned object, an internal combustion engine rotating position detecting device of the present invention comprises a magneto-electric converter element for output an electric signal corresponding to a magnetic intensity, and a magnet for generating a magnetic field. The internal combustion engine rotating position detecting device is characterized by a detected rotating body made of a magnetic material having an irregularity, and a position of the irregularity on the detected rotating body is converted into a rectangular wave-form electric signal. A rotating position of the detected rotating body is detected based on a building-up signal or a falling signal of the rectangular wave-form. Further, the internal combustion engine rotating position detecting device by detecting a width between building-up positions or falling positions of two rectangular wave-forms.
In one current embodiment of the present invention, the internal combustion engine rotating position detecting device employs a magneto-electric converter element in the form of a differential type element having a plurality of magnetic-sensing portions, and the irregularity of the detected rotating body is formed by projections or grooves.
Further, the internal combustion engine rotating position detecting device uses a number of the projections or the grooves arranged on the periphery of the detected rotating body equal to an amount of necessary information, and the projections or the grooves are arranged in a unit of an adjacent pair. In the internal combustion engine rotating position detecting device in accordance with the present invention having such a construction, the magnetic-sensing portion of the magneto-electric converter element and the projection or the groove of the detected rotating body repeat facing and not-facing by rotation of the detected rotating body. A magnetic field generated by the magnet is varied by repeated facing and not-facing, and the magnetic flux density acting on the magneto-electric converter element is varied by the change of the magnetic field. The change of the magnetic flux density is converted into a rectangular wave-form, and then a rotating position of the detected rotating body can be output as an electric signal by detecting building-up positions or falling positions of the two successive rectangular wave-forms.
Generated magnetic flux density is varied by variation of the air gap based on a spacing between a position of the magnetic-sensing portion of the magneto-electric converter element and a position of the projection or the groove of the detected rotating body, and the width (period) of the rectangular wave-form is varied by the variation of the generated magnetic flux density. However, a plurality of magnetic-sensing portions are provided in the magneto-electric converter elements, and a plurality of magnetic flux densities detected by the plurality of magnetic-sensing portions are calculated to bring a building-up position or a falling position of the rectangular wave-form to nearly the same position even if there is difference in the air gaps. Thereby, it is possible to detect positions unaffected or less effected by the air gap.